This invention pertains generally to hand-held power tools, such as spiral cutting tools, and accessories therefore, and more particularly to adjustable depth guides for setting the depth of cut to be made by such power tools.
A spiral cutting tool is a hand-held power tool having an electric motor that rotates a spiral cutting tool bit at high speeds. A spiral cutting tool bit includes a sharp cutting edge that is wrapped in a spiral around the axis of the bit. The spiral cutting tool bit is designed for cutting perpendicular to the axis of the bit. The electric motor that drives the bit is enclosed in a motor housing. The motor housing is generally cylindrical in shape, with the spiral cutting tool bit extending from one end of the motor housing along the axis of the housing. A spiral cutting tool is used to remove material from a work piece by moving the rotating spiral cutting tool bit through the work piece in a direction perpendicular to the axis of rotation of the bit. A spiral cutting tool is conventionally operated by grasping the motor housing with one or both hands, turning on the electric motor to begin high speed rotation of the spiral cutting tool bit, plunging the spinning spiral cutting tool bit into a work piece, such as a piece of wood, and then moving the cutting tool bit through the work piece in a direction perpendicular to the axis of the spiral cutting tool bit by moving the motor housing in a direction parallel to the plane of the work piece while keeping the axis of the motor housing generally perpendicular to the work piece surface.
Precise control of a cut being made by a spiral cutting tool, or any other hand-held power tool, is dependent upon the tool operator maintaining a firm grasp on the tool. Various methods have been employed to ensure that an operator maintains a firm grip on a hand-held power tool. With extended and continuous operation, the motor housing of a spiral cutting tool can become warm, and cutting tool vibrations may cause an operator""s hands and arms to become fatigued. Extended and continuous use of a spiral cutting tool by grasping the motor housing can, therefore, become uncomfortable, reducing the ability of the operator to control precisely the cut being made. U.S. Pat. No. 5,813,805, issued to Robert K. Kopras, describes a detachable handle for spiral cutting tools and other similar hand-held power tools. The detachable handle provides for extensive continuous use of the power tool while maintaining operator comfort and cutting tool control. The handle may be attached securely to the spiral cutting tool when the tool is to be used for extended periods of time, or generally to enhance the operator""s comfort and control in using the spiral cutting tool. The handle may be removed from the tool, for example, when the spiral cutting tool is to be used in tight quarters wherein the handle might become an obstacle to precise control of the spiral cutting tool. The handle is removably secured to the spiral cutting tool by threaded knobs that are inserted through mounting holes in the ends of the handle and tightly threaded into threaded holes formed in handle lugs extending from the motor housing. The threaded knobs are preferably designed so that the detachable handle may be secured tightly to the handle lugs by hand, without the need for a wrench or other tool. The detachable handle also features compartments formed therein for holding various spiral cutting tool accessories, such as extra spiral cutting tool bits and a wrench for securing the bits to the spiral cutting tool.
To set the depth of a cut to be made by a spiral cutting tool, or other hand-held power tool, the tool is typically provided with a depth guide. The depth guide typically includes a depth guide base, which is attached to the power tool housing via one or more depth guide shafts. The depth guide shafts are attached to the power tool housing so as to be slidably movable with respect thereto, thereby allowing the depth guide base to be moved into positions of various distances from the tool, to set various cut depths. A locking knob is typically provided as part of the depth guide which, when tightened, typically by hand, prevents movement of the depth guide shafts and, therefore, movement of the base portion of the depth guide with respect to the tool. To set a depth of cut using such a depth guide, the locking knob is first loosened, to allow movement of the depth guide shafts. The depth guide base is then moved into the desired position to establish the desired depth of cut by moving the depth guide shafts relative to the power tool housing. Markings may be provided, e.g., on the depth guide shafts or on a mechanism attached thereto, to assist in establishing the correct desired cut depth. When the depth guide base is positioned in the desired position, the locking knob is manually tightened, to prevent further movement of the depth guide shafts, and, therefore, of the depth guide base. When locked into position, the bottom of the depth guide base provides a surface which is placed against a work piece to be cut, with a cutting bit extending below the surface by a desired amount corresponding to the depth of cut.
Cutting debris, such as sawdust, can accumulate in the base of a conventional depth guide, around the point of a cut, as the tool to which the depth guide is attached is used to make a cut. The accumulated debris can obscure the point of the cut, i.e., the point where a cutting bit enters a work piece, thereby interfering with accurate use of the tool.
What is desired is a depth guide for setting the depth of cut of a spiral cutting tool, or similar hand-held power tool, which is more easily and rapidly operable than conventional depth guides as described above. What is also desired is a device for removing effectively cutting debris from the base of a depth guide for a hand held power tool.
The present invention provides a depth guide for setting the depth of cut of a spiral cutting tool, or similar hand-held power tool, which automatically locks into a desired position to set the depth of a cut without requiring manual operation of a locking knob or similar structure. The depth guide is released from the locked position by actuation of a release switch. Thus, a depth guide in accordance with the present invention is more easily operable than conventional hand-held power tool depth guides. A depth guide in accordance with the present invention may be mounted in a handle of a hand-held power tool, such as a detachable handle, for mounting the depth guide to a housing of the tool.
An automatic locking depth guide in accordance with the present invention includes a base portion, a depth guide shaft attached to the base portion, and an automatic locking and release mechanism coupled to the depth guide shaft. The automatic locking and release mechanism allows limited sliding movement of the depth guide shaft, automatically prevents movement of the depth guide shaft when the shaft is moved into a desired position to set a desired depth of cut, and releases the shaft from the locked position, to allow motion of the depth guide shaft, in response to the actuation of a release switch. By moving the depth guide shaft in extending and retracting directions, the depth guide base is moved away from and toward a hand-held power tool to which the depth guide is attached, thereby adjusting the depth of cut to be made by the tool. In accordance with the present invention, the depth guide shaft is preferably biased into an extended position, e.g., by a compression spring. The automatic locking and release mechanism preferably includes a mechanism for automatically locking the depth guide shaft into a locked position by preventing movement of the depth guide shaft in an extending direction while allowing movement of the depth guide shaft in a retracting direction. A depth adjustment mechanism for setting one or more depths of cut is provided for preventing movement of the depth guide shaft in a retracting direction beyond a selected amount. The depth of cut for a spiral cutting tool, or other hand-held power tool, may be established using a depth guide in accordance with the present invention by first setting the depth adjustment mechanism to set a desired depth of cut and then simply moving the tool to which the depth guide is attached toward the depth guide base, i.e., by moving the depth guide shaft in a retracting direction, until the depth adjustment mechanism prevents further movement of the depth guide shaft. At this point, the automatic locking mechanism will lock the depth guide shaft into position, preventing further movement thereof, and, thereby, establishing the desired depth of cut. The tool may then be used to make a cut of the desired depth by placing a bottom surface of the depth guide base against a work piece to be cut, with a cutting bit extending below the bottom surface of the depth guide base by a selected amount established by the position of the depth guide, to make a cut of the desired depth. The depth guide shaft may be released from the locked position, to allow motion of the depth guide shaft into an extended position, by actuation of the release switch.
A depth guide in accordance with the present invention is preferably adapted to be attached to the housing of a spiral cutting tool, or similar hand-held power tool. For example, a depth guide in accordance with the present invention may be mounted in a handle attached to the tool housing. Preferably, the automatic locking and release mechanism and depth guide shaft are mounted in a detachable handle which is securely attachable to, and removable from, the housing of a spiral cutting tool or other hand-held power tool. The depth guide shaft is preferably mounted such that it extends from a lower portion of the detachable handle, with the depth guide base attached thereto so as to extend at a right angle from a lower portion of the shaft around the position of, e.g., a spiral cutting tool bit attached to the spiral cutting tool, i.e., around the point of a cut to be made by the spiral cutting tool. The release switch is preferably mounted near the top of the tool handle, for easy operation by an operator of the tool to release the depth guide shaft from a locked position. The depth adjustment mechanism may be implemented as an adjustable depth adjustment screw mounted in the handle and extending therefrom and a depth adjustment stop, e.g., attached to the depth guide base and/or depth guide shaft, and positioned to contact the depth adjustment screw when the depth guide shaft is moved in a retracting direction, thereby to prevent movement of the depth guide shaft in a retracting direction beyond a selected amount. The depth adjustment stop may be movably mounted around the depth guide shaft and provide a plurality of stop positions that are individually moveable into alignment with the depth adjustment screw. A height adjustment mechanism, e.g., a screw threaded into an aperture formed in the stop position of the depth adjustment stop, may be used to predefine a depth of cut at each depth adjustment stop position, thereby predefining a plurality of cut depths to which the depth guide may be adjusted.
The depth guide base preferably has a depth guide base aperture formed therein. A cutting bit attached to the tool to which the depth guide is attached extends through the depth guide base aperture below the bottom surface of the depth guide base, to cut a work piece at the desired depth established by the depth guide. Cutting debris, e.g., sawdust from a work piece being cut, may collect and build up in the depth guide base around the depth guide base aperture during use, thereby obscuring the point of a cut. The present invention provides a dust collector for removing such cutting debris from the depth guide base. The dust collector includes an outer wall, a top wall attached to a top edge of the outer wall, and a conduit attached to either the outer or top wall of the dust collector and extending therefrom. The dust collector is adapted to be attached to the depth guide base by positioning the outer wall of the dust collector on or within the depth guide base. The top wall of the dust collector includes an aperture formed therein. When the dust collector is positioned in the depth guide base, the aperture in the top wall of the dust collector is aligned with the cutting bit attached to the tool to which the depth guide is attached, such that the cutting bit passes therethrough. The outer wall and top wall of the dust collector define a space between the work piece and the dust collector around the point of a cut being made by the tool. Vacuum suction provided to the conduit pulls the cutting debris from this space through the conduit, to thereby clear the cutting debris away from the point of a cut, and thereby preventing cutting debris which may obscure the point of cut from building up in the depth guide base.
Further objects, features and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.